time profligate and unable to control his passions. He said too that the wise man was not exempt from all passions, but indulged them in moderation. He defined friendship as an equality of reciprocal good-will, including under the term as one species the friendship of kinsmen, as another that of lovers, and as a third that of host and guest.¢. The end of love was not merely intercourse but also philosophy. According to him the wise man would fall in love and take part in politics; furthermore he would marry and reside at a king’s court. Of three kinds of life, the contemplative, the practical, and the pleasure-loving life, he gave the preference to the contemplative. He held that the studies which make up the ordinary education are of service for the attainment of virtue. In the sphere of natural science he surpassed all other philosophers in the investigation of causes, so that even the most insignificant phenomena were explained by him. Hence the unusual number of scientific notebooks which he compiled. Like Plato he held that God was incorporeal; that his providence extended to the heavenly bodies, that he is unmoved, and that earthly events are regulated by their affinity with them (the heavenly bodies). Besides the four elements he held that there is a fifth, of which the celestial bodies are composed. Its motion is of a different kind from that of the other elements, being circular. Further, he maintained the soul to be incorporeal, defining it as the first entelechy [7.e. realization] of a natural organic body potentially possessed of life.’ By the term realization he means that which has an incorporeal form. This realization, according to him, is twofold.